A
diet of soy may enhance the effects of tamoxifen, which is used to prevent
breast cancer in high-risk women.

In
a study conducted in rats, researchers at the University of Illinois
at Chicago found that tamoxifen alone reduced the number of carcinogen-induced
tumors by 29 percent, from an average of 7.9 per rat to 5.6. Similarly,
soy alone reduced the number of tumors by 37 percent.

But
when the two were combined, the overall reduction in number of tumors
was 62 percent.

"While
we do not know whether these results apply to women who, because of
environmental factors or genetic predisposition, are at high risk for
developing breast cancer, our study would suggest that a human trial
is warranted," said Andreas Constantinou, associate professor of surgical
oncology at UIC and associate director of research in the Functional
Foods for Health Program, a joint project of UIC and the University
of Illinois at Urbana-Champaign. The results of the study were reported
at the annual meeting of the American Association of Cancer Research
in New Orleans on March 28.

Constantinou
and colleagues are now studying whether the additive effects of soy
seen in this animal study are due to compounds known as phytoestrogens
or to other components of soy.

Breast
cancer is currently the most common cancer in women. It is estimated
that over 800,000 cases and 400,000 deaths occur each year worldwide.
The disease has a clear genetic component, such as mutations in the
BRCA1 or BRCA2 genes. But on a population basis, the major risks are
due to lifestyle and environmental factors, such as poor dietary habits
and exposure to carcinogens. Diet is estimated to contribute to up to
50 percent of all newly diagnosed breast cancer cases.